Hydraulic pumping apparatus



y 21, 1968 R. E. RAYMOND 3,384,029

HYDRAULIC PUMPING APPARATUS Filed Oct. 12, 1965 4 SheetsSheet 1INVENTOR. ROBERT ERAYMOND ATTORNEYS May 21, 1968 R. E. RAYMOND 3,384,029

HYDRAULIC PUMPING APPARATUS Filed Oct. 12, 1965 4 Sheets-Sheet l.

INVENTOR. ROBERT E. RAYMOND ATTORNEYS y 21, 1968 R. E. RAYMOND 3,384,029

HYDRAULIC PUMPING APPARATUS Filed Oct. 12, 1965 4 Sheets-Sheet 5INVENTOR. ROBERT E.RAYMOND BY J ATTORN y 21, 1968 R. E. RAYMOND3,384,029

HYDRAULIC PUMPING APPARATUS Filed Oct. 12, 1965 4 Sheets-Sheet 4 FIG. 8

INVENTOR. ROBERT E. RAYMOND ATTORNEYS United States Patent 3,384,629HYDRAULIQ PUMPING APPARATUS Robert E. Raymond, Zanesville, Ohio,assignor to Hydro-Kinetics, Zanesville, (Ehio Filed Oct. 12, 1965, Ser.No. 495,168 12 Claims. (Cl. 103-173) ABSTRACT OF THE DISCLOSURE Ahydraulic pumping mechanism that includes a housing with two separateoutlet ports, an inlet port, and a control inlet port. Within thehousing, a pressurized outlet chamber is isolated from an inlet chamberwhich communicates with the housing inlet port. A cylinder barrelassembly is slideably mounted within the housing and is provided with aplurality of circumferentially spaced cylinders having a cam drivenpiston disposed in each cylinder. Each cylinder includes two separatecylinder outlets. The first outlet communicates with an outlet manifoldformed in the barrel which in turn communicates with one of the housingoutlet ports and the second outlet communicates with the outlet chamberthat surrounds the barrel which in turn communicates with the otherhousing outlet port. Each piston includes an intake port whichcommunicates with a passage or cavity formed in the piston which in turncommunicates with the interior of the cylnder. A ball-check valve andvalve seat assembly is disposed within the piston to permit only theingress of fluid through the intake port. An annular piston and cylinderare disposed in the housing in force transmitting relationship with thebarrel to control the relative displacement of the pistons in thecylinders. During variable displacement operation, the flow through thesecond outlet varies with the required flow to the load and performs acooling function as it passes through the outlet chamber in heattransmitting relationship with the barrel. When the barrel positionremains stationary, two fixed displacement outlet flows are deliveredthrough each of the separate housing outlets in any proportion desiredas determined by the relative axial spacing of the cylinder outlets withrespect to the piston stroke.

The present invention relates generally to hydraulic machines and inparticular to a novel piston type pumping apparatus.

In general, the pumping apparatus of the present invention comprises asuitable housing, cylinder means provided with two separate outlets andpiston means disposed in the cylinder means and including inlet portmeans communicating with the cylinder means. Fluid is taken into thecylinder means through the piston inlet means on the suction stroke andthen is discharged through the separate cylinder outlets duringdifferent portions of the compression stroke thereby providing inessence two pumps in one.

In accordance with the present invention, the novel pumping apparatuspermits two separate outlet flows in which flow from one cylinder outletmay be delivered to a load while the other outlet feeds a second circuitto circulate a cooling flow to cool the pump. This is particularlyadvantageous in variable displacement operation during high pressureholding periods when the pump is deadheading. The flow in the secondcircuit provides very efiicient cooling of the first circuit.

As another aspect of the present invention, the novel pumping apparatusof the present invention permits two separate outlet flows from one setof pistons which can function as two distinct fixed displacement pumps.The flow from the separate outlets can be divided in any manner bysimple adjustment of the piston stroke relative to the position of thecylinder outlets in the cylinder.

.As another aspect of the present invention, the novel pumping apparatuspermits one pumping apparatus to function as a low pressure, high volumepump in a conventional high-low pump system. Low pressure is unloaded toone circuit as the high pressure circuit builds up and then the lowerpressure circuit circulates to cool the high pressure circuit in thepump.

As another aspect of the present invention, the novel pumping apparatusmay incorporate a cylinder barrel cartridge assembly wherein thecylinders, pistons, and valve means are an integral assembly and may bemanufactured in a convenient pumping package for use in a variety ofhousing envelopes for many different applications. A standard sizecartridge may be employed to reduce inventory and provide easy access toreduce maintenance costs.

As still another aspect of the present invention, the novel pumpingapparatus permits in variable displacement operation, one outlet circuitto be controlled for variable flow with the excess flow being deliveredto another outlet circuit depending upon the position of the othercylinder outlet relative to the piston stroke at any instant.

As a further aspect of the present invention, the novel pumpingapparatus may be manufactured and fabricated at relatively low cost dueto the simplicity of construction and the lack of relatively closetolerance requirements.

It is, therefore, an object of the present invention to provide anapparatus of the type described which provides two separate cylinderoutlets in conjunction with one set of piston means to permit the oneset of pistons to function as two separate pumps.

It is another object of the present invention to provide an apparatus ofthe type described which provides a bypass cooling circuit in additionto the main load circuit to permit efiicient cooling of the pump With noloss of efiiciency in maintaining load pressures.

It is another object of the present invention to provide an apparatus ofthe type described which may be incorporated in a cylinder barrelcartridge assembly to permit manufacture of a convenient pumping packagefor use in a variety of housing envelopes to meet the requirements of awide selection of applications.

It is still another object of the present invention to provide anapparatus of the type described which incorporates an outlet valveconstruction for use with the previously mentioned separate cylinderoutlets to permit a convenient, compact construction, easilymanufactured and fabricated at low cost using standard procedures.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred form of embodiment of the invention isclearly shown.

In the drawings:

FIG. 1 is a side sectional View of a pumping apparatus constructed inaccordance with the present invention, the section being taken along avertical plane through the centerline of the apparatus;

FIG. 2 is a side view of a pumping cartridge assembly constructed inaccordance with the present invention, the remainder of the apparatusbeing shown in section as seen in FIG. 1;

FIG. 3 is a side sectional view of a portion of the apparatus shown inMG. 1 illustrating a check valve for the cooling outlet port in thehousing, the section being taken along a vertical plane through thecenterline of the apparatus;

FIG. 4 is a side view of a portion of the valve assembly shown in FIG.3;

FIG. 5 is an end view of that portion of the valve assembly shown inFIG. 4;

FIG. 6 is a side sectional view of a portion of the apparatus of thepresent invention illustrating the novel piston and piston inletconstruction, the section being taken along a vertical plane through thecenterline of the piston;

FIG. 7 is a diagrammatic view of a typical closed circuit cooling systemwherein the fluid may be forced through an oil filter to clean the fluidbefore returning to the pump inlet port; and

FIG. 8 is an end sectional view of the pump of FIG. 1, the section beingtaken along the line 8-8 of FIG. 1.

Referring in detail to the drawings, a variable displacement pumpconstructed in accordance with the present invention is illustrated inFIGS. 1 and 2 and comprises a housing indicated generally at thatincludes a front housing portion indicated generally at 22 and a rearhousing portion indicated generally at 24. The housing portions arejoined together at the central portion of the pump and held by aplurality of studs 26.

A drive shaft 28 is mounted in the forward end of the housing by taperedroller bearing assemblies 30 and 32 which are pressed into recesses 34and 36.

An oil seal 38 is pressed into a recess 40 in housing 20 and includes anannular resilient element 42 that wipes the periphery of drive shaft 28.

As seen in FIG, 1, the inner end of drive shaft 28 carries a cam meansindicated generally at 44 which includes a central bore 46 provided witha keyway 48 that receives a key 50 for preventing rotation of cam means44 relative to shaft 28. The cam means is retained on shaft 28 by a nut52 which is tightened into locked relationship on a threaded inner endof shaft 28.

With continued reference to FIG. 1, cam means 44 includes an inclinedsurface 54 which engages a plurality of nylon shoes 56, the latterincluding sockets 58 which form pivotal ball joints with ball-shapedends 68 formed on a plurality of pumping pistons 62.

Each of the nylon shoes 56 is surrounded by a metal casing 64 that iscrimped around the ball-shaped end 60 of its respective piston 62. Eachmetal casing 64 also includes an inwardly extended annular protrusion 66that snaps into an annular recess 68 formed in the base of the nylonshoe portion.

With continued reference to FIGS. 1 and 2, a cylinder barrel cartridgeassembly indicated generally at 70 is axially slideably mounted withinhousing 20 and guided by a plurality of guide grooves 72 which receivelongitudinally extending bearing members 76.

Members 76 may best be described as side rail bearings and function notonly to absorb piston side thrust reaction imposed on barrel 70 but, inaddition, bearing members 76 function as keys against cylinder barrelreaction and thereby serve to absorb torque.

Pistons 62 are disposed in respective barrel cylinders 78 which receivelow pressure oil or hydraulic fluid in a novel manner via housing inletport 80, passage 84 in front housing portion 22, an inlet chamberindicated generally at 86 within housing 20 and barrel inlet passages 88formed in each piston 62.

Now referring to FIGS. 1 and 6, inlet ports 88 in pistons 62 communicatewith a cavity 71 formed in each piston 62 which in turn communicateswith a respective cylinder 78 through an orifice 73 in the rearward endof piston 62.

Each of the pistons 62 is provided with an intake valve means formed bya ball-check valve 75 is freely carried in the opening to cavity 71between a valve seat portion 77 and a stop portion 79 formed in eachpiston 62.

On the suction stroke of the pistons 62, fluid is drawn into arespective cylinder 78 via the passage and inlet means described aboveas the low pressure fluid forces ball-check valve 75 away from seatportion 77 to allow fluid to flow into cavity 71 and then throughorifice 73 into cylinders 78.

Now referring to FIGS. 1 and 2 each cylinder 78 includes a unique outletport construction whereby a first cylinder outlet port 81 is disposed ina side wall of each cylinder 78 and a second cylinder outlet passage 83is axially spaced from outlet port 81 and formed in the rearward end ofcylinders 78.

It is important to point out that the axially spaced cylinder outlets 81and 83 may both be disposed in a side wall of cylinder 78 withoutdeparting from the spirit of the invention although the structure shownis preferred. Further, the inlet port may also be formed in the cylinderinstead in the pistons as shown in the preferred embodiment withoutdeparting from the spirit of the present invention.

As seen in FIGS. 1 and 2 each of the cylinders 78 includes a respectivereaction plug, indicated generally at in free self-aligning engagementwith the inner end surface 92 of rear housing portion 24.

Each reaction plug 99 is provided with a central bore 94 that carries apressure responsive outlet valve means formed by a ball check valve 96which is freely retained in bore 94 by a threaded plug 98.

Each threaded plug 98 includes a seat portion 100, a second barreloutlet passage 102, and a radial passage 103, the latter communicatingwith an annular passage 104 formed in the outer wall of reaction plug98.

With continued reference to FIG. 1, bore 94 in each reaction plug 98includes a valve stop 106 and a compression spring 108 which serve tolimit the stroke of the ball and bias its toward a closed position.

A plurality of pressure responsive valves 87, attached to the outersurface of barrel 70 by screws 89, covers each of the first cylinderoutlets 81 and is in the form of a substantially flat, flexiblereed-type valve. Pressure responsive valves 87 is normally biased in aclosed position and the degree of valve opening is limited by a stiffback-up plate 91 attached by screws 89 to pressure responsive valves 87.

It is important to point out that the reed-type valves 87 are preferredbecause they provide eflicient valve means and yet conveniently take uplittle space. Further, valves 87 are easily incorporated into thecylinder barrel cartridge assembly 70 to provide an integral package tooffer the attractive commercial advantages previously mentioned.

It should be pointed out that the cylinder wall openings for the firstbarrel outlet passages 81 are each valved by their respective pistons 62and will be referred to herein as piston position responsive valves forsaid first barrel outlet passages.

Pressurized fluid from cylinders 78 is first discharged on thecompression stroke of the pistons 62 through first cylinder outlet 81,the fluid forcing pressure responsive valves 87 open, and flows into anoutlet chamber or cooling chamber 93 formed in rear housing portion 24.Outlet chamber 93 is isolated from the inlet fluid in inlet chamber 86by an annular seal engaging barrel 70 and an annular cylinder barreldriving piston, indicated generally at 146 which will be described indetail later herein.

Outlet chamber 93 completely surrounds cylinder barrel assembly 70 andforms a passage means for the outlet flow of fluid through a check valve220 disposed in a housing outlet port 222 formed in the rear housingportion 24.

As best seen in FIG. 1, as a piston 62 advances during the compressionstroke, outlet passage 81 is closed by the outer wall of cylinder 78 andflexible reed valve 87 will close.

It is important to point out that the flow through outlet passage 81depends upon the position of barrel 70, hence passage 81, relative tothe stroke of piston 62. Further, since the fluid from outlet passage 81flows completely around barrel 70, a very effective cooling flow isdeveloped.

When piston 62 advances to the position where outlet passage 81 isclosed, the pressurized fluid is then discharged through the secondcylinder outlet port 83 through second barrel outlet passages 102 inreaction plugs 90, a plurality of small radially extending passages 103,annular recesses 104, annular manifold 134, barrel outlet port 122,radial passages 112, an outlet member 110, passage 114 and a secondhousing outlet port 116 to the load.

Hollow outlet member 110 includes the central passage 112 thatcommunicates with high pressure discharge passage 114 that in turn leadsto housing outlet port 116.

As seen in FIG. 1, outlet member 110 also includes a foot portionprovided with a surface 118 that is in slideable sealed engagement witha longitudinally extending surface 120 formed in the outer wall ofcylinder barrel 70.

It will be noted from FIG. 1 that when cylinder barrel 70 is axiallyshifted relative to the housing means 20 an outlet port 122 formed inthe cylinder barrel always remains in communication with central passage112 in outlet member 110 notwithstanding axial movement of cylinderbarrel 7 0.

With continued reference to FIGS. 1 and 2, pressure biased outlet member110 includes a piston surface 124 that causes the pressurized hydraulicfluid in passage 112 to bias the surface 118 on outlet member 110downwardly into sealed engagement with longitudinally extending surface120 on barrel 70. If desired, outlet member 110 can be structurallymodified so as to be hydraulically balanced in accordance with theteachings in my co-pending application Serial No. 594,350.

A spring 126 augments the biasing force of the high pressure oil onpiston surface 124 and also serves to retain surface 118 in sealedengagement with surface 120 at low pressures and at the outset ofoperation.

The outer peripheral surface of outlet member 110 is provided with anannular seal 128 and a threaded plug 129 is screwed into the holeforming passage 112 and includes an inner protrusion that forms aretainer for the end of spring 126.

Pressurized oil is also released to a variable displacement hydrauliccontrol unit indicated generally at 135 by a second pressure biasedoutlet member 110A, FIGS. 1 and 2, which is substantially identical tooutlet member 110 previously described. It will be noted that outletmember 110A includes a base surface 136 that is hydraulically biasedint-o sealed engagement with a longitudinally extending surface 138formed in the outer wall of cylinder barrel 70. Outlet member 110A isbiased downwardly against longitudinally extending surface 138 by aforce exerted by a piston surface 124, pressurized oil in a passage 140.

Referring to FIG. 1, cylinder barrel 70 is constantly biased towards thefront of the housing means by a control spring 142 which is interposedbetween a spider 143 and an annular shoulder 145 formed on cylinderbarrel 7 0.

Cylinder barrel 70 is hydraulically shifted axially against the biasingforce of control spring 142 by an annular cylinder barrel driving pistonindicated generally at 146 in FIG. 1. Piston 146 is mounted in acylindrical surface 148 and forms therewith control cylinder 150 forreceiving pressurized oil in a manner later to be described. A smallannular piston surface 152 of large diameter provides suflicient axialforce with low control pressures to shift cylinder barrel 70 against theforce of control spring 142.

With continued reference to FIG. 1, piston 146 includes a rear end 155in force transmitting engagement with annular seal which in turn is inforce transmitting engagement with an annular base portion 157 oncylinder barrel cartridge 70.

Referring particularly to FIGS. 1 and 8 pressurized oil is deliveredthrough control apparatus to control cylinder via outlet port 122-A,passage 140, passage 144, orifice 147, radial passages 130 in spoolhousing 151, lateral passage 154 in control block 156, longitudinalpassage 158 in control block 156, vertical passage 160 in control black156 and passage 162 in housing 20 which connects to control cylinder150.

Referring particularly to FIGS. 1 and 2 spool housing 151 carries alongitudinally shiftable spool member 164 that is normally biasedtowards a closed position by a spring 166, the latter being contained ina spring housing 168 that is threaded into control block 156 at athreaded hole 170. Compression spring 166 is selectively compressed orcompressed by manipulating a control knob 172 that includes a shank 174in threaded engagement with spring housing 168 at a threaded hole 176.As seen in FIG. 1, a radial passage 178 communicating with passage 162in housing 20 provides a direct drain back to tank for any fluid thatmay flow back from control cylinder 150 during shock conditions.

As best seen in FIG. 8, control block 156 is mounted on housing 20 by aplurality of studs 192. It will be understood that other types ofcontrol apparatus responsive to various load conditions can be readilyadapted to replace control apparatus 135.

The pumping pistons 62 are returned and biased against cam means 44 by asingle centrally disposed piston return rod 194, FIG. 1, which includesan arcuate socket 196. A ball 198 fits into socket 196 of rod 194 andalso into a socket 200 formed in a piston return yoke 202. Yoke 202includes a plurality of radially extending slots 204 that fit aroundneck portions 206. Piston return y-oke 202 applies force to the rearsides of the ball-shaped piston ends 60 and in turn receives force frompiston return rod 194 via the pivot joint formed by ball 198 and sockets196 and 200. A compression spring 210 is disposed between a shoulder 214on the rear end of piston return rod 194, a shoulder 214 on a springretainer plug 216 which in turn bears against the front side of spider143. Spider 143 is restrained from rearward movement by the shoulders224 formed on the ends of reaction plugs 90. It should be pointed outthe reaction plugs 90 are fitted loosely into respective holes 91 inspider 143 and are in free engagement with the inner surface 92 of thehousing whereby the plugs are self-aligning with respect to pumpcylinders 78.

In operation, when the pumping apparatus is driven by a prime mover, cam44 reciprocates pistons 62 which, on the suction stroke draw fluid intocylinders 78 via inlet port 80, inlet passage 84, inlet chamber 86,barrel inlet passages 88, cavity or passage 71, and orifice 73.

It is important to point out the inlet port means may be disposed in thecylinders 78 themselves instead of in pistons 62 without departing fromthe spirit of the invention.

The intake fluid forces ball-check valve 75 away from seat portion 77 asit enters passages 88 and fiows through cavity 71 and out of orifice 73into cylinders 78.

On the suction stroke, valves 87 are normally biased in a closedposition.

On the compression stroke, fluid is delivered first through firstcylinder outlet passages 81 as the flexible valves 87 are forced openwith the degree of opening being limited by back-up plate 91. The amountof flow through passages 81 depends upon the position of passages 81relative to the stroke of pistons 62 which in the variable displacementpump illustrated, varies according to the position of barrel 70. Fluidthen flows into and through outlet chamber 93 to housing outlet port 222and out one way check valve assembly 220, best seen in FIGS. 3, 4, and5.

Referring to FIGS. 3, 4, and 5, check valve 220 is biased against avalve seat portion 226 by a spring 228 and prevents fluid from flowingback into outlet chamber 93.

ressurized fluid from cylinder outlets passages 81 flows through chamber93 and forces valve 220 open to permit fluid to flow out of housingoutlet port 222.

Many types of conventional valves or surge control orifices may be usedin place of outlet check valve 220 to prevent flow back through port 222on the suction stroke of pistons 62.

The fluid from port 222 may then be delivered to a load or recirculatedfor cooling purposes. A typical closed circuit cooling system isillustrated diagrammatically in FIG. 7.

The fluid from port 222 leads to a heat exchanger 260 and then is forcedthrough a very fine filter 262 before returning to reservoir 250. Thefluid from reservoir 250 is pulled through a conventional wire screenfilter 252 to inlet port 80. Therefore, the oil circulated through thepump housing 29 is cooled and cleansed before returning to the interiorof the housing. It is important to point out that a substantial flowthrough cylinder outlet passages 81 occurs which is delivered out ofoutlet port 222 to provide very eflicient cooling of the hydraulicsystem.

After the wall of piston 62 passes outlet passage 81, the remainder ofthe pressurized fluid flows through second cylinder outlet port 83 tothe other housing outlet port 116 via passages 102 in plugs 90, checkvalves 96, radial passages 103, annular grooves 104, manifold 134,passage 112 in hollow outlet member 110 and outlet passage 114 whichleads to outlet port 116.

The fluid in inlet chamber 86 is isolated from the fluid in outletchamber 93 by annular seal 95.

Some of the pressurized oil in manifold 134 is delivered to variablecontrol apparatus 135 for shifting annular piston 146 and cylinderbarrel 70 as previously mentioned.

A constant pressure at the load is obtained by arranging spool 164 toopen only when a predetermined selected load pressure is exceeded.Control knob 172 is adjusted to compress spool control spring 166 so asto bias spool 164 with the proper force to permit its opening when thepredetermined selected operating pressure is exceeded. When the pressureat the load rises above the operating pressure oil from the manifoldpasses through passage 144 and orifice 147 to spool cylinder 149. Theincreased pressure in the spool chamber overcomes the preset controlforce exerted by spool control spring 166 whereby the spool is shiftedto the left, as viewed in FIG. 1, and oil is released through radialpassages 130 in spool housing 151 and thence through the previouslydescribed passages to the control cylinder 150. This shifts annularpiston 146 and cylinder barrel 70 to the left as viewed in FIG. 1,whereby cylinder outlet passages 81 are moved to the right relative tothe pistons 62. This movement increases the flow of fluid throughpassages 81 because said passages are closed later in the compressionstroke whereby more oil is free to fiow out of said ports. Accordingly,this decreases the flow of oil per piston compression stroke out ofsecond cylinder outlets 83 to automatically cut back the pressure inthat circuit.

When the pressure drops to the preselected control pressure the biasingforce exerted by spool control spring 166 shifts spool 164 to the right,as viewed in FIG. 1, whereby the spool closes radial ports 130 and theflow of oil to control cylinder 150 is terminated.

It is important to point out that the present invention has beendescribed only by Way of illustration, with respect to variabledisplacement operation and a cooling circuit but is not limited to suchan application.

The pumping apparatus may be readily adapted to perform as two fixeddisplacement pumps with both housing outlet ports 116 and 222 connectedto a load. The cylinder barrel 70 may be fixedly positioned to dividethe flow between outlets 81 and 83 in any manner desired or a variableflow control may be used to control one circuit with the excessdelivered to the second circuit.

It is also important to point out that other valve means than the typeshown may be employed such as, for example, an orifice which permitssubstantial flow in only one direction may be used to replace valves 87and outlet passage 81, particularly for recirculating cooling fluid,without departing from the spirit of the present invention.

I claim:

1. In a variable displacement axial type pump, the combination of ahousing including a housing inlet port and first and second housingoutlet ports; an axially shiftable cylinder barrel disposed in saidhousing and including a cylinder provided with axially spaced first andsecond barrel outlet passages, a piston mounted for reciprocation insaid cylinder, and a barrel inlet passage; intake valve means carried bysaid barrel for said inlet passage whereby fluid enters said cylinder onthe suction stroke and fluid is discharged first from said first barreloutlet passage and one of said housing outlet ports during a portion ofthe compression stroke of said piston and then through said secondbarrel outlet passage and the other of said housing outlet ports duringa subsequent portion of said compression stroke, said first barreloutlet passage including a piston position responsive valve and apressure responsive valve; and a pressure responsive outlet valve meansfor said second barrel outlet passage whereby fluid is diverted throughsaid first barrel outlet passage to cool said pump during operatingconditions of reduced flow through said second barrel outlet passage.

2. The apparatus defined in claim 1 wherein said barrel inlet passageand intake valve means are in said piston.

3. The apparatus defined in claim 1 wherein said pressure responsivevalve for said first barrel outlet passage consists of a reed-typevalve.

4. The apparatus defined in claim 1 wherein one of said barrel outletpassages is disposed in a side wall of said cylinder barrel and theother of said barrel outlet passages is disposed in the pressurized endof said cylinder.

5. In a variable displacement axial type pump, the combination of ahousing including a housing inlet port and first and second housingoutlet ports; an axially shiftable cylinder barrel disposed in saidhousing and including a plurality of cylinders, each of said cylindersincluding a first barrel outlet passage in a side wall of said barreland a second barrel outlet passage, pistons mounted for reciprocation insaid cylinders, an annular manifold communicating with said secondbarrel outlet passages, and barrel inlet passages communicating withsaid cylinders; intake valve means carried by said barrel for said inletpassages whereby fluid enters said cylinders on the suction strokes andfluid is discharged first from said first barrel outlet passages and oneof said housing outlet ports during portions of compression strokes ofsaid pistons and through said second barrel outlet passages, saidannular manifold, and the other of said housing outlet ports duringsubsequent portions of said compression strokes, each of said firstbarrel outlet passages including a piston position responsive valve anda pressure responsive valve; and a pressure responsive outlet valve foreach of said second barrel outlet passages whereby fluid is divertedthrough said first barrel outlet passages to cool said pump duringoperating conditions of reduced flow through said second barrel outletpassages.

6. The apparatus defined in claim 5 wherein said barrell inlet passagesand intake valve means are in said pistons.

7. The apparatus defined in claim 5 wherein said pressure responsivevalves for said first barrel outlet passages consist of reed-typevalves.

8. The apparatus defined in claim 5 that includes a hollow outlet memberradially shiftably mounted in said housing and provided with an innersurface slidably engaging the outer surface of said cylinder barrel forthe passage of pressurized fluid from said annular manifold to saidother of said housing outlet ports.

9. The apparatus defined in claim 5 that includes an annular cylinderbarrel driving piston for axially shifting said cylinder barrel, and anannular seal between said barrel driving piston and said barrel, saidseal serving to separate an inlet chamber in said housing from anannular cooling chamber in said housing.

10. The apparatus defined in claim 5 that includes a hydraulicallyactuated control cylinder in said housing; an annular cylinder barreldriving piston disposed in said control cylinder for varying thelocation of said first barrel outlet passages relative to said pistons.

11. The apparatus defined in claim 5 wherein said barrel includes aplurality of axially extending guides; and a plurality of bearingmembers disposed between said guides and said housing.

12. The apparatus defined in claim 5 that includes a plurality ofreaction plugs carried by said barrel and having inner ends disposed insaid cylinders and outer ends freely engaging said housing, said secondbarrel outlet passages and pressure responsive outlet valves beingdisposed in said reaction plugs.

References Cited UNITED STATES PATENTS 2,620,733 12/1952 Overbeke 1031612,990,781 7/1961 Tuck et a1. 10337 3,024,731 3/1962 Heintz 103373,050,014 8/1962 Sullivan 103--162 3,067,694 12/1962 Fancher 1031733,145,660 8/1964 Bush 103202 X 3,183,847 5/1965 Raymond 103-1733,249,052 5/1966 Karlak 103-173 DONLEY J. STOCKING, Primary Examiner.

WILLIAM L. FREEH, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION- Patent No.3,384,029 Dated May 21, 1968 Robert E. Raymond Inventor(s) It iscertified that error appears in thQabove-identified patent and that saidLetters Patent are hereby corrected as shown below:

In Fig. 1, reference numeral 130 has been added with a lead line to thedottedpassage communicating passages 130 and 162. In Fig. 8, referencenumeral 124 has been deleted and 110-A inserted therefor. In Fig. 2',reference numeral 92 has been added with a lead line to the barrelsurface represented by reference numeral 92 in Fig. 1. Column 6, cancellines 13 31 and substitute der 150 via cylinder block outlet passage1221A, passage 140 in outlet member llO-A, passage 144, orifice 147 anda radial passage v130 that connects with a housing passage 162 which inturn connects with control cylinderlSO as seen in Fig. l.

With continued reference to Fig. l, a control spool 149 is axiallyslideably mounted in a spool housing 151 and is biased toward a leftposition by compression spring 166 in which position spool 149 normallyisolates radial passage 130 from control orifice 147.

When the fluid pressure through control orifice 147 exceeds apredetermined pressure value, established by the selected setting of acontrol knob 172 that includes a shank 174 in threaded engagement with aspring housing 168 at a threaded hole 176, then spool 149 shifts to theright thereby overcoming spring 166 via self-aligning spool end 164.Radial passage 130 is thereby opened and pressurized fluid is releasedto control cylinder 150 as explained above. This serves to shiftcylinder block 70 to the left, Fig. l, to a new position of equilibriumwherein the force exerted on the cylinder block by compression spring142 equals the force exerted on said block by annular control piston146.

Referring again to Fig. 1, a radial passage 178 in the pump housingprovides a drain from the control apparatus 135 back to the relativelylow pressure outlet chamber 93. When pressure of oil through orifice 147acting on the end of spool FORM M050 uscoMM-oc wan-Poo i U S. GOVEIHHNI'IIHYING OT'ICI I... 0-3..3!

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.,384,029 Dated May 21, 1968 PAGE Z Inventor-(s) Robert Raymond It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

149 drops belowthe preset value established by control spring 166, thenspool 149 shifts to the left closing passage 130 to pressurized flow andsubsequently opening passage 130 to drain passage 178 in the pumphousing via passages 154, 158 and 160. This permits annular controlpiston 146 to move to the right discharging fluid from annular chamber150 back to low pressure outlet chamber 93. This permits the cylinderblock to shift to the right to a new position of equilibrium.

Signed and sealed this 30th day of May 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. I ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

